SHORTLY AFTER THE PLT TOOK OFF ON A NGT FLT TO BETHEL, THE ACFT CRASHED JUST NORTH OF THE EAST/WEST RWY IN A NOSE DOWN ATTITUDE & ON A SOUTHWESTERLY HEADING. THE ACFT WAS DESTROYED DURING IMPACT, BUT CONTD SLIDING APRX 35 YDS TO THE NORTH EDGE OF THE RWY, THEN OVERTURNED & CAME TO REST ABOUT 120 FT FROM THE INITIAL IMPACT POINT. AN INVESTIGATION REVEALED THE ACFT HAD LANDED AT SOME TIME BTN 2300 & 0015 ADT. AT ABOUT 0030, THICK FOG FORMED IN THE VICINITY OF THE ARPT WHICH WAS LOCATED BESIDE A RIVER. REPORTEDLY, THE ACFT TOOK OFF ABOUT 5 MIN PRIOR TO THE ACDNT (APRX 0055 ADT). AT ABOUT THE TIME OF THE ACDNT, A WITNESS ON A RIVER BARGE SAW AN ACFT FLYING ALONG THE RIVER, HEADING TOWARD THE ARPT. THE WRECKAGE WAS NOT FND UNTIL APRX 0900 WHEN ANOTHER ACFT WAS TAXIING TO TAKEOFF. THE PLT HAD PURCHASED SOME ALCOHOLIC BEVERAGES & WAS TRANSPORTING THEM IN THE ACFT. THE SEAL OF 1 BOTTLE WAS BROKEN, BUT THE BOTTLE WAS ALSO BROKEN. A CHECK OF THE PLT'SBLOOD SHOWED ONLY A TRACE OF ALCOHOL WHICH COULD HAVE BEEN ATTRIBUTED TO PUTREFACTION.